Hi. I normally use OBD2 to manage my car.
Build a program is not difficult but, as you write, is not fast to do.
Have you got the OBD2 protocol? I know that a lot of commands are not available and you have to have them to implement in the software...

Hi! So first if I'm wondering - are you looking for advice, to hire someone, freelance work, or what.. just curious why you posted on the jobs forum as otherwise this might not really be the right place for your post.

Anyways, I'm looking for a job or anything right now but your project does sound pretty interesting. Do you have a blog or something you might update with progress?

When I was at university worked on a project doing something pretty similar - I took the stock system out of a vehicle and retrofitted a touchscreen, an imx6sabre-auto board, and various other bits and bobs. What I did was connect it through to the vehicle's CAN system. I'm curious when you say that the car has OBD-II but not CAN as most relatively modern vehicles do have CAN, and in fact pins 6 & 14 are can-low and can-high. Plus all vehicles sold in the US after july 2008 were actually required to have CAN. Just mentioning this because if the vehicle has CAN, it might be a lot easier to interface with depending on the board you're using - arduino has can shields for instance. OBD-II boards definitely exist too though and OBDII messages are more standard, but there tends to be a lot more information on the CAN bus if you're willing to play around with things to see what messages they spit out.

When I built the UI for my sytem I used QtQuick, which worked really well once I actually got it compiled, running, and getting commands from the touchscreen I was using (much easier said than done). If you go that route you'll have to create an interface from CAN/OBD-II through to QML.

If you have any questions you think I might be able to help with feel free to ask - you'll probably be running into a lot of the same problems I did along the way.

Another thing - as you'll be running your board from the vehicle's 12V system, make sure the board can stand fluctuations in the voltage level. I'd sometimes get voltage drops and even though I was using an automotive-specific board they caused havoc (mostly during startup). Then again, the electical system on the car my board was connected to had to deal with power supply sometimes coming from an inverter connected to a high-voltage system with 2 electric motors and a battery bank, so you might not run into the same problems. But when you crank the motor the voltage will drop significantly, but not necessarily enough to black out the board.